This disclosure relates to a milling tool for machining a workpiece. The disclosure relates, in particular, to a milling tool which is suitable for producing a cyclo-palloid toothing.
Cyclo-palloid toothings are frequently also designated as Klingelnberg cyclo-palloid toothings. Such toothings can be found in the majority of cases on bevel gears or other gearing parts. Compared to bevel gears with “regular”, straight toothings, bevel gears with cyclo-palloid toothings are distinguished by their greater smoothness, better acoustics, higher load capacity and better utilization of the installation space.
The tooth shape of a cyclo-palloid toothing corresponds to the portion of a spiral. The teeth consequently each comprise a convex and a concave flank, the width of each tooth widening along the tooth comb. The one end-face end of each tooth is therefore narrower than the other end-face end of the same tooth on account of the spiral-shaped widening.
Due to the geometry, the production of such cyclo-palloid toothings is more complex and consequently in most cases more expensive when compared to “regular” toothings with straight flanks. Cyclo-palloid toothings are usually produced by means of gear-cutting machines which are set up especially for this purpose. On account of the high purchase costs of such gear-cutting machines, however, increasingly there is the desire to produce such geometrically complex toothings also by means of universal milling machines. This is of interest in particular to producers that produce these types of bevel gears, also called hypoid bevel gears or spiral bevel gears, in small batches as for such producers the purchase of an extra gear-cutting machine is not really profitable.
There are already approaches for the construction of special milling tools by means of which abovementioned toothings can be produced on CNC milling machines with five-axis technology. The results obtained with the previously known solutions of such special milling tools have up to now been rather modest from a qualitative and economic view point. This is in particular due to the relatively long machining time which comes about as a result of a relatively high number of machining steps being necessary with the previous milling tools in order to mill the tooth profile to be produced on the workpiece to the full depth thereof. On account of the relatively complex geometry of the toothing, it has not been possible, up to now, to mill at least parts of the toothing profile directly to the full profile depth in one operation as the plunge depth is restricted on account of the geometry in order to avoid collisions between tool holder and workpiece. In addition, frequently more than only one tool is also necessary in order to produce the tooth profile of a cyclo-palloid toothing by means of milling.